This invention relates to a device for sensing the operative status of an electrical apparatus unit which is provided with an AC-DC converter, the sensor being adapted to distinguish between conditions of operation and non-operation (including a standby condition).
In prior art devices, the operating condition of an electrical apparatus unit has been sensed by detecting the presence of an electric current supplied to the unit or by detecting whether an amount of an electric current is in excess of a reference value or not. However, different electrical apparatus units are different in their electric current consumption according to classes and conditions of use thereof. Further, various apparatuses are each different in operating electric current and non-operating electric current modes, such as, for example, those that use a small flow of electric current in order to place the apparatus in a standby condition (for example, a television set having a preheat function). For example, there is one type of electrical apparatus which consumes only a minute amount of electric current even though it is in an operating condition, while there are others which consume an electric current more than the aforesaid minute amount of electric current to maintain the apparatus in a standby condition. Therefore, conventional sensing devices, which detect the operation or non-operation of electrical apparatus merely from the presence or magnitude or an amount of electric current, cannot be employed with devices for which the reference values must be adjusted or in which partial power consumption must be distinguished from normal operation.